HSV­TK/GCV can induce cytotoxicity of retinoblastoma cells through autophagy inhibition by activating MAPK/ERK.

ABSTRACT

Retinoblastoma is an severe ophthalmic disease and the most common type intraocular malignant tumor, particularly in infants. Currently, few drugs and therapies are available. Gene therapy has been considered to be a potential treatment to cure cancer effectively and Herpes simplex virus type 1 thymidine kinase/ganciclovir (HSV­TK/GCV) is one type of suicide gene therapy that has been extensively studied. Numerous in vitro and in vivo studied have shown that this system can kill tumor cells, including liver and lung cancer cells. GCV is used as an antiviral drug, and the thymidine kinase, HSV­TK can phosphorylate GCV to GCV­TP, a competitive inhibitor of DNA synthesis, instead of guanine­5'­triphosphate in the process of DNA synthesis. This process prevents DNA chain elongation causing cell death via apoptosis. However, the toxic effects of HSV­TK/GCV on retinoblastoma cells remain unknown, and the molecular mechanisms of its therapeutic effects have not been fully elucidated. Our results suggest that HSV­TK/GCV can significantly cause the death of retinoblastoma cell lines, HXO­RB44 and Y79. Further studies have reported that this cell death is induced by the inhibition of autophagy by activating the MAPK/ERK (mitogen­activated protein kinase/ERK) signaling pathway. The mTOR inhibitor Torin1 can partially block the toxic effects of HSV­TK/GCV on HXO­RB44 cells. The above results demonstrate that the mechanism undertaken by HSV­TK/GCV to exhibit therapeutic effects mechanism may inhibit autophagy by activating MAPK/ERK. The findings of the present study may provide novel insight for the exploration of HSV­TK/GCV in the treatment of retinoblastoma.